1. Field of the Invention
This invention relates to an elastic coupling mainly for use in an automotive vehicle, etc. where it is interposed between drive shafts and driven shafts to transmit a torque while absorbing a vibration, torsion, etc. between both shafts.
2. Description of the Related Art
At a power transmission part of an automobile such as drive shafts, propeller shafts, etc. an elastic coupling having a vibration damping function is used as a coupling for transmitting a torque from the drive shafts to driven shafts.
The elastic coupling is, as exemplified in FIG. 5 and FIG. 6, made up of a plurality of drive side collars (101) adapted to be connected to drive shafts and a plurality of driven side collars (102) to be connected to driven shafts, e.g. drive shafts, both arranged alternately on a concentric circle, endless belt-like fiber bundles (103) each wrapped between adjacent collars in a multi-layer and multi-row, and an elastic material (104) such as rubber, synthetic resin, etc. covering and surrounding these collars (101)(102) and the belt-like fiber bundles (103), thereby being configured as an annular form of a generally polygon or circle.
The aforesaid drive side and driven side collars (101)(102) are each formed with a plurality of flange parts (112)(122) for holding the belt-like fiber bundles 103 on outer peripheral surfaces of cylindrical parts (111)(121). The collars (101)(102) are press-fitted to respective inner cylinder members (105)(106), through which the drive side collars (101) and the driven side collars (102) are, when in use, fixed to drive shafts at their axial ends and to driven shafts at their axial ends, respectively by means of a fastening mean such as bolts, thereby serving to transmit power while absorbing a vibration, etc.
Stated another way, the elastic coupling of this type is capable of elastically deforming in areas between the drive side and the driven side collars (101)(102) embedded in the elastic material (104) and accordingly, serves to perform the power transmission while absorbing a vibration, torsion, etc. in the axial direction generated between the drive shafts and driven shafts by the elastic deformation of the elastic material (104).
For the purposes of rendering such an elastic coupling as stated above more light-weight, recently, it has been considered to use an aluminum-containing metal material such as aluminum, its alloys, etc. for the respective drive side and driven side collars thereby to integrally form them by a casting means such as die casting, etc.
Where the collars are a die cast product made of an aluminum metal material, however, the die cast product singly cannot ensure a sufficient strength required for use. Consequently, it is a general practice to close fit the collars, when in use, by press fitting to respective inner cylinder members.
For an interference upon press fitting as stated above, if the interference value is such that an inner periphery of each collar and an outer periphery of each inner cylinder member are fitted together in an overall axial length of the both, a resistance to the press fitting extends to the overall length and a significant press-fitting force is required. As a result, not only is the press fitting work troublesome, but also a shaving powder can be produced upon press fitting. In that case, there is the danger that the shaving powder clings to inner peripheral surfaces of the cylindrical parts of the collars thereby obstructing the press fitting work to result in a bad press fitting.
On the other hand, if the aforesaid interference value is made smaller, the fit force by press fitting will full short. As a consequence, a large vibration weight is loaded in the axial direction during use, so that where a high load is generated in the belt-like fiber bundles, there occurs a danger of positional deviation or disconnection of the inner cylinder members from the collars.
In view of the problems above, the present invention has been made, and it is an object of the invention to provide an elastic coupling, in which it is possible to press fit the drive side and driven side collars easily, securely and firmly to respective inner cylinder members with a sufficient interference; which can be used without the danger of deviation or disconnecting; and whose durability and reliability can be enhanced.
This invention relates to an elastic coupling comprising a plurality of drive side cylindrical collars each adapted to be connected through an inner cylinder member to a drive shaft and a plurality of driven side cylindrical collars each adapted to be connected through an inner cylinder member to a driven shaft, both arranged equidistantly and alternately on a concentric circle, endless belt-like fiber bundles each wrapping around adjacent drive side cylindrical collar and driven side cylindrical collar, and an elastic material embedding therein both the collars and the belt-like fiber bundles, the drive side collars and the driven side collars having respective cylindrical parts and plural flange parts, for holding the belt-like fiber bundles, integrally formed on outer peripheral surfaces thereof, the inner cylinder members being fitted in the cylindrical parts of the drive side and driven side collars. The coupling is characterized in that the cylindrical parts of the drive side and driven side collars are formed, in axially central areas on inner peripheral surfaces thereof each as a radially expanded portion from the other portion of each of the inner peripheral surfaces.
According to the elastic coupling, because of the fact that the radially expanded portions are formed in axially central areas on the inner peripheral surfaces of the collars, no resistance to press-fitting is created at the radially expanded portions when the inner cylinder members are press fitted into the cylindrical parts of the collars on their inner peripheries, and even if a shaving powder is produced upon press fitting, it intrudes into the radially expanded portions, without obstructing the press fitting and consequently, press fitting can be performed fairly easily. Besides it is possible to conduct the press fitting securely with a sufficient interference at both axial end portions other than the radially expanded portion.
In a state of use where the drive side collars and the driven side collars are connected respectively to drive shafts and driven shafts, the step formed between the radially expanded portion and the other portion on the inner periphery of the cylindrical part of each of the collars serves as a hook to an axial deviation of the press-fitted inner cylinder members in cases where a high load occurs in the axial direction owing to a vibration, etc., as a result of which any axial deviation and disconnection can be avoided, thus maintaining a good press-fit condition.
With the elastic coupling stated above, it is preferred that the cylindrical parts of the collars and the inner cylinder members be close fitted together by press fitting; and an inside diameter difference between the radially expanded portion and the other portion on the inner peripheral surface of each cylindrical part be set larger than an interference value for press fitting of the inner cylinder members to the cylindrical parts. Thereby it is possible to perform the press fitting easily and firmly without causing any press-fit resistance at the radially expanded portions on the inner peripheries of the collars as stated above.
Preferably the flange parts on the outer periphery of each collar assume a taper form such that the thickness of each flange part gradually tapers down from a base portion to an external edge thereof whereby axial rigidity of the flange parts can be ensured sufficiently even if the collars are an integrally molded product made of a light-weight metal such as aluminum or Al-containing metal.